The high/low microbial abundance (HMA/LMA) dichotomy in sponges has been the subject of
several studies over recent years, but few studies have analysed this dichotomy in terms of the
sponge archaeal community and function. Using a 16S rRNA gene barcoded pyrosequencing
approach and predictive functional analysis (PICRUSt) we compared the archaeal
composition, richness and predicted function of one HMA sponge (Xestospongia testudinaria),
one LMA sponge (Stylissa carteri) and one sponge species of unknown microbial abundance
(Aaptos lobata). Although most of the archaeal sequences were assigned to the
Crenarchaeota phylum, S. carteri had the highest percentage of sequences assigned to the
Euryarchaeota phylum. Variation among sponge species explained >85% of the variation in
archaeal operational taxonomic unit (OTU) composition with each sponge species forming a
distinct cluster. There were significant differences in predicted PICRUSt profiles among
sponge species, suggesting that archaeal communities present in the studied sponge species
may perform different functions. X. testudinaria and A. lobata were similar both in terms of
OTU and KEGG orthologues composition, which may indicate that A. lobata is a HMA
sponge. Additionally, some of the most enriched functions seem to be related to traits
associated with high and low microbial abundance sponges.publishe